#app3{}
#app3 > .square{
    border: 1px solid rebeccapurple;
    height: 10vw;
    width: 10vw;
    position: relative;
    top: 50%;
    left: 5%;
    margin-top: -5vw;
    transition: 1s;
}

#app3 > .square.active{
    border-radius: 50%;
    transform: translateX(35vw);
}